Epsilon Archive for Student Projects

Abstract

Spatial and social systems form the organisation of animals in space and time and are
important aspects of animal ecology due to their effect on population dynamics and
structure. In this study I investigate territorial dynamics of female wolverines, with
particular focus on interannual territorial fidelity and reoccupation of territories vacated due
to death of territorial females. To do this, I used location data and den site locations of adult
female wolverines (n = 58), collected from 1993-2008 in and around Sarek National Park,
northern Sweden.

I found that female wolverines exhibited high interannual fidelity to territory. Resident
females (n = 34) were monitored for a total of 145.9 wolverine years, and only twelve
females moved from their territories one or more times during the study, resulting in a total
of 14 vacated territories. Hence, 9.6% of resident females moved from their territories
annually. Fifty-eight percent of the females (n = 7/12) that abandoned their territories
established new territories, with a mean distance of 11.7 km between dens in their old and
new territories.

Sixteen (70%) of territories vacated due to death of a resident female (n = 23) were
reoccupied by a replacing female. The mean territory overlap between the deceased female
and her replacer was 75% (range 57-87). Sixty-nine percent of replacers (n = 16) occupied
vacated territories within a year. There was a new reproduction the first year after the
territory was vacated in 30% of all the vacated territories (n = 23). The time from
reoccupation to first reproduction in the territory was significantly longer for juvenile and
subadult replacers than for adult replacers. I found that 54% of the marked replacers were
daughters and 15% were granddaughters of the deceased female. Every time a daughter
was still present in the territory when her mother died, the daughter occupied the vacated
territory.

My results suggest that the spatial organization of female wolverine territories in
Scandinavia is characterized by long-term stability, as vacated territories are generally
occupied by new individuals rather than absorbed by neighbours. Furthermore, in a
population that is saturated with territories, deceased females are generally replaced by
females from the local population, and primarily daughters if they are still present in the
territory when their mother dies. Hence, local density of territorial females is resumed
while emigration is decreased, which can have implications for adjacent populations. I also
showed that the time from reoccupation to first reproduction for the replacing females
varied considerably. This is important from a Swedish management perspective, as the
local density, and possibly predation pressure, might recover quickly after removal of
territorial females, while the amount of economical compensation, based on number of
wolverine reproductions, to reindeer herding districts for predation losses is reduced until
next reproduction in the territory. My study shows that the reoccupation process and time
to next reproduction, effects on local density and emigration are important factors to
consider when using removal of individuals to decrease predation pressure

The demographic importance of female survival for population growth is further
emphasized by my results, which shows the strong influence of adult female survival on
territorial dynamics and dispersal, and hence its effect on a larger scale.